JP2019126723A - Method and fiber-optical system for illuminating and detecting object with light - Google Patents

Abstract

An optical fiber bundle calibration and an object observation using an optical fiber bundle are performed at an original position.
Kind Code: A1 The present invention provides in-situ calibration of a fiber bundle (3) and illumination detection of an object (9) with turbulence-corrected light, in particular for application to endoscopes and microscopes. The invention relates to a method and a fiber-optical system. The present invention can directly determine the single-phase distortion of light due to transmission by the fiber bundle, as compared to the prior art, which measured double-phase distortion for calibration of the fiber bundle (3) So that the system function of the fiber bundle (3) can be determined. The system function is used to correct the light disturbance when illuminating and detecting the object (9).
[Selected figure] Figure 1

Description

  The present invention relates to methods and fiber-optic systems for illuminating and detecting objects with light, particularly for endoscopic and microscopic applications. The invention includes in-situ calibration of a fiber-light image waveguide (fiber bundle) and illumination or detection with light distortion correction.

  A fiber-optic system in the form of a flexible endoscope (soft mirror) comprises a large number (100, 000) of individual flexible optical fibers, for example glass fibers. Optical image transmission is feasible if the individual fibers of the fiber bundle are arranged coherently. The advantages compared to rigid endoscopes (rigidscopes) in which the image information is transmitted via the rod lens system are in particular the compactness of the ultra-fine fiber bundle and in particular when access to the object to be observed is very limited. It is in flexible use. The disadvantage of flexible mirrors is that the achievable image contrast is relatively low. This is in particular due to fiberisation of the fiber bundle, crosstalk between the individual fibres, loss of image sharpness (blur effect) and multi-modality of the lightwave induction in the individual fibre (speckle effect). The degradation of the image quality due to the above mentioned disturbance of the light from the fiber bundle can be explained by the modulation transfer function. Furthermore, flexible fiber bundles are only allowed for the transmission of intensity profiles and their imaging with lenses (near field technology). Because the optical path lengths of the individual fibers are different and unknown, it is not possible to directly grasp the phase information of the transmitted light, and thus the far field of the transmitted light is unknown and not specifically adjustable.

  Reducing the pixel spacing of the image obtained with the use of a soft mirror means imaging optics, generally imaging the distal surface of the fiber bundle onto the object object plane, generally a plurality of optical lenses Alternatively, it can be achieved by integrating an imaging optical member such as a lens system. However, this significantly increases the installation size of the soft mirror, thus increasing the minimum size for optical access. Furthermore, complex construction and connection techniques, as well as multiple adjustment steps are required to integrate the imaging optics. A further disadvantage arises from the fact that fiber bundles with conventional imaging optics are only capable of two-dimensional measurement in the outer surface (sagittal). In order to obtain depth information, for example, the scanning method uses mechanically displaceable optical elements or electrically adjustable optical systems, or other complex measuring methods (using two fiber bundles). Must be done using the

  Various techniques exist to correct light distortion caused by transmission through optical waveguides. Patent Document 1 describes a method for correcting polarization dependent disturbances in an optical waveguide, the compensation function of the polarization dependent disturbances being calculated by the optical waveguide, the electrical input signal initially distorted by the function Is calculated. This electrical input signal is the signal which is intended to be transmitted via the optical waveguide and which is converted into a corresponding distorted optical input signal. To determine the compensation function, a detector configured to measure signal to noise ratio, polarization dependent attenuation or mode dispersion, bit error rate, or signal dispersion is used.

  In the adaptive optics methods known from the prior art, (optical) wavefront sensors and modulators can be used to detect and equalize phase aberrations. Such a method for beam control of high energy laser beams is disclosed, for example, in US Pat. Non-Patent Document 1 describes an adaptive optical method including an open control loop called "digital optical phase conjugation", which is suitable for correction of phase distortion due to passage of an optically opaque, particularly biological medium. Has proposed. In this method, a CCD camera is used as a sensor, and a spatial light modulator (SLM) is used as an actuator. The method disclosed in Non-Patent Document 1 requires each pixel of the camera to generate a virtual image (virtual image) on the corresponding pixel of the SLM, and vice versa. As a result, this method requires complex calibration and very sophisticated adjustment work. Non-Patent Document 2 describes an endoscope that includes a flexible multimode fiber that can be calibrated using a partial reflector at the distal end and an SLM at the proximal end. In the range described in Non-Patent Document 2, calibration of such an endoscope and measurement using an endoscope can not be performed simultaneously. Here, the terms "proximal" and "distal" characterize the positional relationship with respect to the fiber bundle, with the proximal side of the fiber bundle being the end face facing the illumination source and the distal side of the fiber bundle facing the end face Suppose that

  U.S. Pat. No. 5,959,095 describes a flexible mirror that can change the relative phase of incident light using an SLM placed at the proximal end of the fiber. The phase difference caused by the fiber with respect to the incident light is determined by a wavefront sensor or interferometer. For this purpose, a partially reflective coating is applied to the distal fiber end. As a result, the phase difference Δφ is determined after the light has passed through the fiber bundle twice, so it is not a single phase difference that is measured, but instead 2Δφ, each 2π. The disadvantage of measuring double retardation is that this measurement is unclear. For example, if a double retardation for π is measured, the single retardation caused by the fiber bundle may be π / 2 or −π / 2. A true single phase difference can only be determined using complex methods.

  Patent Document 4 proposes to illuminate the multimode waveguide in the distal direction using a virtual light source image with respect to the above disadvantages. A multimode fiber with a double coating and containing a single mode fiber core is considered, at the distal end of which a holographic photographic material and a point reflection generating object (thereby a virtual light source is generated behind the object) Be placed. In the case of illumination, the (light) waves transmitted by the single mode fiber contribute to the outcome of this method by interfering with the light emitted from the virtual light source at the location of the photographic material. This method has the disadvantage that the position of the virtual light source is fixed and can not be freely selected, so that the position selection for the actual focus is also greatly restricted. Furthermore, specific optical designs are required at the distal end of the fiber.

International Publication No. 2004/032386 German Patent No. 60223130 US Pat. No. 8,855,587 US Patent Application Publication No. 2015/015879

Cui, M.C. and Yang, C.I. Implementation of a digital optical phase conjugation system and its application to study The robustness of the suppression by phase conjugation, Optics Express 18, Vol. 4 (2010), page 3444 Gu, R. Y. , Mahalati, R. N. and Kahn, J.A. M. , Design of flexible multi-mode fiber endoscope, Optics Express 23, Vol. 21 (2015), page 26905

  The subject of the present invention is therefore an improved method of correcting disturbances caused by transmission through a bundle of optical fibers in the light emitted from an illumination source, and the fiber-optics associated with this method. It is to propose a system. The proposal also includes eliminating the need for repetitive execution of complex adjustment steps for system calibration. In other words, it is contemplated that a bundle of optical fibers can be used as a coherent phased array of light ("remote phased array").

  The object of the present invention is achieved by a method having the technical features as claimed in claim 1 and a fiber-optical system having the technical features as claimed in claim 9. The inventive scope of the invention is set forth in the dependent claims.

  The method of illuminating and detecting an object using light according to the present invention comprises calibrating an coherent fiber of an optical fiber and illuminating the object with a turbulence-corrected light or detecting a turbulence-corrected light And comprising. The coherent optical fiber bundle, for example a plurality of glass fibers, is preferably flexible. The calibration in method step a) is used to at least identify and evaluate the system function of the fiber bundle and may be represented by a transfer matrix between the proximal end and the distal end of the fiber bundle. System functions are also referred to in the literature as "transfer functions". In the method step b), the determined light disturbance is largely compensated for in the observation of the object. The disturbance may be visualized, for example, as distortion of the wave front of the light or deformation of the wave field. Observation of an object includes illuminating the object and detecting the object.

  By means of the method according to the invention, the calibration of the fiber bundle and the observation of the object by means of the light whose light disturbance has been compensated for can advantageously be carried out in situ, e.g. The changes in system functions caused by the system can be grasped immediately without complicated manual adjustment.

  A trimmed fiber bundle is referred to as a "coherent" fiber bundle if in each case the positional relationship between the two fibers of the bundle remains constant over the entire length of the bundle. Hereinafter, the positional relationship with respect to the fiber bundle is often characterized by the terms "proximal" and "distal". The proximal side of the fiber bundle is the end surface facing the illumination system, and the distal side of the fiber bundle is the end surface facing the object.

The method of the present invention comprises the following sub-method steps for calibrating the fiber bundle in method step a):
i) Illuminate from the proximal at least one freely selectable individual fiber in the coherent bundle of optical fibers.
ii) Reflect the light at least partially in the partially reflecting means located away from the distal end face of the bundle of optical fibers. This illuminates the region of the fiber optic bundle comprising two or more individual fibers from the distal end by the reflected light. The reflected light is light corresponding to light diverging from a virtual image of each illuminated fiber.
iii) detecting the spatial intensity distribution of reflected light transmitted and disturbed through the distal illuminated region of the fiber optic bundle, or through the distal illuminated region of the fiber optic bundle The spatial intensity distribution of the interference pattern generated by interfering the reference wave with the transmitted wave disturbed is detected.
iv) Evaluating the detection data to at least directly extract a single phase difference ΔΦ of the reflected light transmitted and disturbed through the distally illuminated area of the bundle of optical fibers.
v) Determine a system function that reflects the transmission characteristics of the distal illuminated region of the fiber optic bundle.
vi) Repeat method steps i) to v) to determine a system function that reflects the transmission characteristics of the entire fiber optic bundle.

  In order to calibrate the fiber bundle, the fact is used that the light guided through the individual fibers of the fiber bundle is reflected by the partially reflecting means on the face of the partially reflecting means not facing the fiber bundle. Ru. That is, it is possible to consider that a virtual image (virtual image) of an individual fiber is produced on the distal surface of the fiber bundle, and that the reflected light is coming from a substantially point-like virtual source. From the virtual light source, distal illumination (individual fibers) is thus generated, and the number of fibers illuminated from the distal end of the fiber bundle depends on the distance between the virtual light source and the distal end face of the fiber bundle. Dependent. The use of a near point virtual light source is similar to the astronomical guide star concept, and in the following, the near point virtual light source will be referred to as a "guide star".

  In sub-method step iii) is detected a spatial intensity distribution of the reflected light, ie the light being disturbed by being transmitted through the area of the fiber bundle illuminated from the distal end by the virtual light source? Alternatively, an interference pattern generated by coherent superposition of the transmitted and disturbed light by the distally illuminated area of the fiber bundle is detected. In this case, according to the invention, in order to illuminate the distal end of the fiber by the guiding star, the detected data is replaced by a double phase difference 2 · ΔΦ, as in the case of purely illuminating the proximal part of the fiber , Which enables extraction of a single phase difference ΔΦ.

  In principle, illuminating the single fiber of the fiber bundle from the proximal side, and the partially reflecting means at the distal end face of the fiber bundle, so that the guiding star occurs at a distance large enough to illuminate the whole fiber bundle It is possible to arrange it sufficiently away from The lower method step vi) may then be omissible if the system function reflecting the transmission characteristics of the entire optical fiber bundle has already been determined by the lower method steps i) to v). However, if the distance between the partially reflecting means and the distal end of the fiber bundle is large, imaging errors may occur and adversely affect the quality of the calibration. The method according to the invention is such that the distance between the partially reflecting means and the distal end face of the fiber bundle is such that only a portion of the fiber bundle around the individual fibers illuminated from the proximal end is illuminated from the distal end Is advantageously applied to be selected. The lower method steps i) to v) may be repeated until a system function reflecting the transmission characteristics of the entire bundle of optical fibers is determined. For this purpose, in the lower method step i), in each case (example) different parts of the fiber bundle are illuminated from the proximal side. Thereby, different portions of the fiber bundle are illuminated from the distal side, each of the different portions is captured at least once, and the system function of the fiber bundle is calculated by combining the system functions of the respective portions. The distance between the partially reflecting means and the distal end face of the fiber bundle may typically be about 100 μm.

  Generating multiple guide stars is advantageous in terms of better calibration with better focus quality. In order to advantageously reduce the time taken for calibration, in one embodiment of the method of the invention, the lower method is such that at least two non-adjacent individual fibers of the bundle of optical fibers are illuminated simultaneously from the proximal side Step i) is performed. Then, in a lower method step ii), at least two virtual images of the individual fibers are obtained from the distally illuminated regions of the fiber bundle where the images do not overlap.

For the purpose of observing the object, the method of the invention comprises the following method step b).
b) Correcting the disturbance of light and illuminating the entire bundle of optical fibers from the light with light, detecting an object placed in the optical path after the partial reflection means, or illuminating the entire optical fiber bundle from the proximal Following the illumination without correcting the disturbance, an object placed in the optical path after the partial reflection means is detected with the disturbance corrected.
Here, the illumination disturbance correction is performed by applying an inverse function of the system function to the light emitted by the illumination system by interaction with a wavefront modulator comprising individually actuable elements. Here, after transmission of a bundle of optical fibers, a wave field approximately corresponding to the light emitted by the illumination system is available for the proximal illumination of an object placed in the optical path after the partial reflection means.
Also here, detection perturbation correction is performed following the interaction with the object, followed by the spatial intensity distribution of the light transmitted and disturbed by the bundle of optical fibers, or following the interaction with the object. The spatial intensity distribution of the interference pattern generated by interfering the reference wave with the disturbed light transmitted by the bundle is numerically modified by applying the inverse function of the system function. It will be.

  After performing the calibration of the fiber bundle in method step a), a calibration function is determined that reflects the transmission characteristics of the entire fiber bundle, so that the correction of the disturbance is taken before or after the object is illuminated by the fiber bundle by the fiber bundle. It is feasible.

  Thus, in order to compensate for the disturbances occurring during the transmission of light through the fiber bundle, the object is illuminated by the wave front pre-distorted by the wave front modulator according to the inverse system function or the fiber after dispersion at the object The disturbance due to the bundle is numerically compensated and illumination is performed using a wavefront that is not pre-distorted. Within the meaning of the present invention, a “wavefront modulator” is to be understood as a device which purposely influences at least one of the phase of the lightwave and the amplitude of the lightwave.

  In an embodiment of the method of the invention, in sub-method step i) at least one freely selectable individual fiber is illuminated proximally by at least one first illumination source, in method step b) Lighting the entire coherent fiber optic bundle from the proximal side, with or without correcting the light disturbance, is performed by the second illumination source. Alternatively, proximal lighting of at least one of the freely selectable individual fibers of the lower method step i) and lighting of the proximal whole of the whole optical fiber bundle with correction or uncorrected disturbances of the method step b) One of these is performed using exactly one illumination source. Here, a wavefront modulator, at least for the purpose of illuminating at least one of the freely selectable individual fibers from the proximal side, the light being arranged in the optical path between the illumination source and the coherent bundle of optical fibers To interact with. In this case, the individually actuatable elements of the wavefront modulator are such that the main part of the light of the illumination source does not hit the fiber bundle but instead only the part used to illuminate at least one of the individual fibers Orientated. According to the above embodiment, it is also advantageously possible to illuminate several non-adjacent individual fibers simultaneously.

  Since the system functions in method step a) and method step b) should be at least substantially identical, the frequency of performing calibration of the fiber bundle is generally according to the characteristic time scale of the light disturbance caused by the fiber bundle. It is determined. In this case, method step a) and method step b) can be performed in any desired sequence. For example, it is a sequence of a)-b)-a)-b) or a)-b)-b)-b)-a)-b)-b)-b). Embodiments of the invention are also suitable, in particular, for simultaneously performing method step a) and method step b), if the correction of the light disturbance of the detection is performed numerically.

  According to one embodiment of the method of the present invention, light is mostly reflected or transmitted at the distal side of the bundle of optical fibers, depending on its wavelength. This design advantageously enables simultaneously calibrating the fiber bundle and observing the object with light of one wavelength that is strongly reflected at the distal end of the fiber bundle. Light of a wavelength that is predominantly reflected at the distal end of the fiber bundle is used for calibration and is used to observe the object. This procedure makes it possible to cleanly separate the detected signal with respect to its optical path based on the wavelength.

  According to a further embodiment of the method of the invention, the light is largely reflected or transmitted distal to the bundle of optical fibers, depending on its polarization state. This design advantageously allows simultaneously calibrating the fiber bundle and observing the object with the fiber bundle. Light of one polarization state, which is largely reflected at the distal end of the fiber bundle, is used for calibration and light of another polarization state, which is mostly transmitted at the distal end of the fiber bundle, observes the object Used to do. This procedure makes it possible to cleanly separate the detected (light) signal with respect to its light path, based on the polarization state.

  A further embodiment of the method according to the invention performs by digital holography the evaluation of the detected data and the extraction of at least the phase information of the reflected light transmitted and disturbed by the distally illuminated area of the fiber bundle. It is characterized by being done. In this case, the spatial intensity distribution of the interference pattern obtained by coherently superimposing the reference wave on the disturbed reflected light is detected and evaluated. The reference wave is particularly preferably generated by beam splitting of the light emitted by the illumination system. Advantageously, digital holography offers the possibility of determining phase information quickly and without complex iterations. The frequency of turbulence correction is substantially limited by the assembly, for example by the frequency at which the elements of the wavefront modulator can be adjusted.

  In a further embodiment of the method of the invention, extraction of at least phase information of the reflected light transmitted and disturbed by the distally illuminated area of the fiber bundle from the evaluation of the detected data and the detected intensity distribution And are implemented by numerical reconstruction using the phase recovery method. For example, the (light) intensity transport equation may be evaluated as requiring the detection of the intensity distribution at at least two different points along the optical path, for the purpose of causing the intensity distribution to be detected. It is also good.

  In a further embodiment, the method of the invention is extended in that a freely adjustable light pattern is generated on the distal side of the fiber bundle, in particular over a wide variable range, which also includes a plurality of focal points. For this purpose, the individually actuable elements of the proximal wavefront modulator are actuated accordingly. Compensation of the light disturbance of the illumination can thereby be performed simultaneously. The ability to focus using a wavefront modulator advantageously provides depth information about the object being viewed. A scan may be performed and this method may be used for application of light, such as an actuator, for example for optical tweezers or radiation therapy.

  In addition to the above method, the invention also relates to the fiber-optical system associated with the method.

  The fiber-optical system according to the invention for illuminating and detecting an object by means of a light comprises an illumination system which is an optical fiber, for example a glass fiber, on which the coherent bundle of optical fibers is illuminated, the fiber bundle preferably being flexible (Flexible).

  The means for partially reflecting the light emitted by the illumination system are observed with a plurality of distal cross sections (facets), ie the end faces of the fibers of the fiber bundle facing the object and away from the illumination system Located in the optical path between the object. The partially reflecting means is separate from the distal cross section, ie not directly adjacent to (eg not deposited on) the distal cross section.

  Furthermore, the fiber-optical system according to the invention may be used to detect the spatial intensity distribution of the light transmitted and disturbed by the fiber bundle, or alternatively to coherently overlap the reference wave with the light transmitted and disturbed by the fiber bundle. A means may be provided for detecting the interference pattern generated together. The disturbance of light may be visualized, for example, as distortion of the wavefront of the light or as deformation of the wavefront.

  Additionally, the fiber-optic system of the present invention may comprise a signal processing platform that at least evaluates the detected data and determines at least phase information of the light transmitted by the fiber bundle to be disturbed.

  In addition to the components described thus far, the system of the invention may also comprise further optical components, in particular a beam splitter, arranged in a convenient manner.

  According to the present invention, the illumination system illuminates at least one of the freely selectable individual fibers in the fiber optic bundle to calibrate the fiber-optic system and detects light to detect the object. It may be designed to illuminate the entire bundle of fibers. In this case, the calibration of the fiber-optic system comprises at least identifying and evaluating the system function of the fiber bundle, this evaluation being performed between the proximal and distal ends of the fiber bundle, in particular the transfer. It may be indicated by a matrix.

  By means of the fiber-optical system according to the invention, both system calibration and object detection and observation can be carried out immediately in situ, where eg due to movement, vibration or temperature change Changes in system functions can be identified instantaneously without complicated manual adjustments.

  As already mentioned in the description of the method according to the invention, the solution according to the invention uses a system function to calibrate the fiber-optical system and correct light disturbances during observation of the object, so that the system function is determined In being substantially based on directly measuring a single phase difference ΔΦ as the light emitted by the illumination system passes (fiber bundle). In the present invention, the inverse of the system function is applied to the proximal illumination of the entire fiber bundle, or the inverse of the system function is used to numerically correct the measured data characterizing the object.

  The fiber-optical system according to the invention can be advantageously used for imaging, in which the resolution in the lateral direction (sagittal plane) is no longer limited by the pixel spacing of the fiber bundle (usually> 3.3 μm) Instead, it is limited only by the numerical aperture of the light guiding fiber core. In this case, a lateral resolution of less than 1 μm can be achieved depending on the diameter of the fiber core.

  The fiber-optic system of the present invention preferably comprises an instrument only on the proximal side of the fiber bundle. There is no need for active or magnifying optics at the distal end of the fiber bundle. Thus, the present invention advantageously enables the manufacture of an ultra-thin endoscope, the diameter of the endoscope at its distal end being substantially determined by the diameter of the fiber bundle.

  In one embodiment of the fiber-optical system of the present invention, the illumination system comprises at least one illumination source and a wavefront modulator comprising a plurality of individually actuatable elements. The wavefront modulator is arranged in the light path between the proximal cross section (facet) of the bundle of optical fibers and the at least one illumination source. For calibration of a fiber-optical system, orient the elements of the wavefront modulator so that at least one freely selectable individual fiber of the bundle of optical fibers is illuminated from the proximal side by at least one illumination source You may The portion of the illumination light not needed to illuminate at least one of the individual fibers is deflected by the wavefront modulator so as not to hit the fiber bundle. Within the meaning of the present invention, the description “at least one of the individual fibers” means that a plurality of nonadjacent individual fibers of the fiber bundle can be simultaneously or sequentially proximally for the purpose of calibration It is also possible to be irradiated. This does not mean that the area around one fiber of an individual fiber comprises multiple fibers, and this area is illuminated from the same time with the one fiber at the same time during calibration. Advantageously, the illumination system described above may be used, particularly simply by activating different elements of the wavefront modulator, for calibration with simultaneous or temporally continuous illumination, for a plurality of individual fibers .

  According to a further embodiment of the system of the present invention, the illumination system may also comprise at least two illumination sources, at least at least one of the freely selectable individual fibers of the fiber bundle for calibration of the fiber-optical system. One may be illuminated by at least one illumination source, and the second illumination source may illuminate all of the bundles of optical fibers to detect an object. In this embodiment, the overall intensity of the illumination source used for calibration is advantageously available.

  For example, a laser may be used as an illumination source.

  In a further embodiment of the inventive fiber-optical system, a wavefront modulator comprising a plurality of individually actuable elements is arranged in the optical path between the proximal end face of the optical fiber of the fiber bundle and the illumination system. The signal is such that the reflection at the elements of the wavefront modulator gives the light emitted by the illumination system and not disturbed by the illumination system to illuminate the object, the reverse of the disturbance caused by the transmission by the bundle of optical fibers. A wavefront modulator is enabled by the processing platform.

  According to a variant of this embodiment of the fiber-optic system of the invention, any light pattern, ie light in which at least one of the spatial intensity, phase and polarization state distribution is freely adjustable over a wide variable range A pattern is generated distal to the bundle of optical fibers by the individually actuatable elements of the wavefront modulator. In particular, the light pattern may have more than one focus. This advantageously enables scanning to be performed using a fiber-optical system and to obtain fiber-optical systems, for example for optical tweezers and radiation therapy, in order to obtain depth information on the observed object. It becomes possible to use as an actuator.

  According to a further variant of this embodiment of the fiber-optic system according to the invention, the wavefront modulator is a digital local spatial light modulator. Local spatial light modulators generally comprise an LCoS, an LCD cell, a component in which any of the micromirrors are arranged on a semiconductor chip, and an application specific integrated circuit, which cells or mirrors operate independently. Possible, at least one of tilting and lowering is possible. In this (variant) case, the spatial light modulator comprises at least one element per fiber of the fiber bundle, ie one micromirror. A ratio of about 100 elements per fiber is common. It is advantageous to be able to change the tilting or lowering of the individual micromirrors very quickly so that they can respond quickly to changes in system function.

  In embodiments of the fiber-optic system according to the invention, the means for partially reflecting the light emitted by the illumination system comprises a reflective surface, the reflectivity of the reflective surface being a function of wavelength or polarization state Or that the reflecting surface is translucent.

  In one embodiment of the fiber-optic system of the invention, the means for partially reflecting the light emitted by the illumination system comprises a reflecting surface, the reflectivity being such that the reflecting surface acts as a wavelength selective beam splitter Is a function of the wavelength of the light to be Within the meaning of the present invention, a wavelength selective reflective surface reflects light of a considerable part of a particular wavelength or wavelength range, and light of a considerable proportion of another particular wavelength or another wavelength range. Used for and through. A multilayer reflective surface that functions in this way is also referred to as a “dichroic filter”. The advantage of this embodiment is that when using two different wavelengths of light, especially light with a small wavelength difference, one wavelength is selected as slightly smaller than the end of the filter and the other is slightly smaller. The calibration of the fiber-optic system and the observation of the object with light with corrected disturbances can be performed simultaneously (in a manner similar to wavelength division multiplexing). As a result, the object is illuminated and measured using at least one wavelength of light that is largely transmitted, and the fiber-optic system is calibrated using light of at least one wavelength that is largely reflected at the same time Ru. Even in the case of speckle decorrelation between different wavelengths, correction can be performed with known dispersion relationships.

  In one embodiment of the fiber-optic system of the present invention, the means for partially reflecting the light emitted by the illumination system comprises a reflective surface, the reflectivity being a function of the polarization state of the light. The reflective surface acts as a polarization state dependent beam splitter (also referred to as a polarization beam splitter), the polarization state of the light (eg right circular polarization) is mostly reflected and the other polarization states (eg left circular polarization) are mostly It is transmitted. As a result, the object is illuminated and measured with light in the predominantly transmitted polarization state, and at the same time the fiber-optical system is calibrated with light in the predominantly reflected state. In the case of the described preferred embodiments, it is advantageous that calibration of the fiber-optical system and observation of the object with the disturbance-corrected light can be performed simultaneously. The precondition for that is that the fibers of the fiber bundle are to maintain polarization. For example, a fiber bundle comprising photonic crystal fibers may be used.

  In one embodiment of the fiber-optic system of the present invention, the means for partially reflecting the light emitted by the illumination system includes a translucent mirror, wherein the “translucent” property is the reflection of light Various configurations of mirrors where the part and the transmitted part are not equal are also included. The light is preferably predominantly transmitted by the semitransparent mirror. Particularly preferably, a part of the light intensity in the single digit percentage range is reflected by the semitransparent mirror and used to calibrate the fiber-optical system, the remaining part is transmitted and used for the observation of the object . In the present embodiment, it is possible to separate the part used for calibration and the part used for observation of the object with the light whose distortion has been corrected, according to the transit time of the light signal.

  The means for partially reflecting the light is separated from the distal cross section (facet) of the fiber bundle. In particular, for example in the embodiments described above, the partially reflecting means are those that are not directly and immediately deposited on the distal cross section of the fiber bundle. The distance from the distal section may be ensured, for example, by a glass spacer, and a reflective surface is applied to the distal end of the spacer. A similar effect is obtained by a plurality of silica glass fibers in a fiber bundle, in which the core is Ge-doped to increase the refractive index, and at the distal end of the fiber a non-doped region with a reflective surface deposited. Prepare. The axial extension of the undoped region specifies the distance between the distal cross-section of the fiber bundle and the means of partially reflecting light.

  In a further embodiment of the fiber-optical system according to the invention, the detection means may comprise a CCD camera or a CMOS camera. In this case, the camera used comprises at least one pixel per fiber bundle. Generally, the ratio is 10 to 100 pixels per fiber.

  In a further embodiment of the fiber-optical system according to the invention, the signal processing platform comprises at least one of an FPGA (field programmable gate array) and an image processing unit (especially using GPGPU = general purpose computing on the image processing unit). Equipped with These components of the digital control system are advantageously characterized by low processing latency.

  It goes without saying that the features and details of the system described by the invention also apply in relation to the method according to the invention and vice versa.

  The invention can be used, for example, in a fiber-optic system intended for imaging an object. An example of this system is an endoscope or a microscope. However, the invention can also be used, for example, in fiber-optical systems, for which laser-guided surgery, cell stimulation or optogenetics simulation are intended. Applications to additive manufacturing are also possible. Of course, this list only partially reproduces many of the many possible uses of the present invention.

  The invention is not limited to the embodiments shown and described but includes all embodiments which function similarly within the meaning of the invention. It is also expedient, as appropriate, to combine the above variants and embodiments according to the invention with the technical features of the claims for carrying out the invention. The invention is not limited to the combination of features specifically described, but on the premise that the individual features are not mutually exclusive or that certain combinations of individual features are not explicitly excluded. It is intended to be embodied by any other possible combination of particular features of all the individual features disclosed.

  While the invention will be described with reference to several embodiments, it should be understood that the invention is not limited to those embodiments.

FIG. 5 is a schematic diagram of determining a system function of a fiber bundle, wherein a detector is disposed proximal to the fiber bundle. FIG. 4 is a schematic diagram for compensating for the system function of a fiber bundle before illuminating an object.

  FIG. 1 shows a schematic diagram of a fiber-optic system 1 that includes a detector 2 on the proximal side 32 of a flexible fiber bundle 3. This figure is intended to show the calibration in the form of an initial measurement of the system function. In this embodiment, the phase information of the light that is distorted by being transmitted by the fiber bundle 3 is determined by digital holography.

  The illumination system comprises an illumination source 4 and a spatial light modulator 6. The light emitted by the illumination source 4 represented by the plurality of flat wavefronts 41 is split in the beam splitter 5 into a portion 51 and a second portion 52 which are reflected towards the spatial light modulator 6 Be done. The second part 52 is transmitted directly to the detector 2 by the beam splitter 5 and functions as a reference wave 21 for holography.

  The individual elements of the spatial light modulator 6 are inclined in such a way that, of the portion 51 of the illumination light, only the portion 61 is reflected towards the fiber bundle 3 in the form of a flat wave, whereby exactly one individual The fiber 30 is illuminated from the proximal. On the distal side 31, the individual fibers 30 may be interpreted as the starting point of the fundamental wave 33, which leaves the substantially point-like individual fiber 30 and is partially reflected by the translucent mirror 7. Are waves directed at least partially to the fiber bundle 30. This is to optically illuminate the fiber bundle consisting of the substantially point-like individual fibers 30 from the distal side 31 by the guide star 8 which is optically generated after the semitransparent mirror 7 and which is a virtual image (virtual image) It corresponds to Finally, therefore, at least one region of the fiber bundle 3 around the individual fibers 30 is illuminated distally by the fundamental wave 33. The size of the area of the fiber bundle 3 thus illuminated from the distal end depends on the distance between the distal cross section (facet) of the individual fibers 30 and the semitransparent mirror 7. FIG. 1 shows an embodiment in which the entire fiber bundle 3 is illuminated from the distal.

  The wavefront 34 disturbed with a single phase difference Δφ by being transmitted by the fiber bundle 3 leaves the fiber bundle 3 from the proximal end 32. These wavefronts are reflected on the detector 2 which may be, for example, a CCD camera. The beam splitter 5 splits at least partially, the reference wave 21 is superimposed on the wave front, and the detector 2 records the interference pattern. To record this interference pattern, the digital information of a signal processing platform (not shown) may be used to extract the phase information of the disturbed wave 34 directly into holographic. The system function representing the transmission characteristics of the fiber bundle 3 may thus be determined in the form of a transfer matrix.

  FIG. 2 is a schematic view of compensating the system function representing the transmission characteristics of the fiber bundle 3 by means of the spatial light modulator 6 before illuminating the object 9. According to the invention, in each case (embodiment) the measurement and evaluation of the system function by the signal processing platform (not shown) takes place before the compensation of the system function. An embodiment for calibrating the fiber bundle 3 is described in FIG. The signal processing platform reverses (inverts) the measured system function and adjusts the individual elements of the spatial light modulator 6. Thereby, the light emitted by the illumination source 4 by the reflection at the spatial light modulator 6 is superimposed on the antiphase (inverted one) of the phase distortion (light disturbance) caused by the fiber bundle 3. The light is again represented by a plane wave 41 in this case and is at least partially reflected on the spatial light modulator 6 by the beam splitter 5. After reflection at the spatial light modulator 6, the wave front 62 has distortion, which is compensated by the fiber bundle 3 during subsequent transmission. A flat, turbulence-corrected wave 35 emerges from the distal end 31 of the fiber bundle. The means for partial reflection arranged in front of the object 9 are not shown for the sake of clarity.

  The individual elements of the spatial light modulator 6 may be arranged such that the phase distortion experienced by the flat wave 51 due to the fiber bundle 3 is compensated. In addition, the arrangement of the individual elements of the spatial light modulator 6 allows light focusing to occur at one or more focal points (not shown) when the light exits the fiber bundle 3 distally. When the flat wave 51 is reflected by the spatial light modulator 6, an inverse system function is applied thereon and focusing occurs. A pre-deformed and focused wavefront (not shown) is then introduced into the fiber bundle 3 where phase distortion is compensated while maintaining focus. A focused, turbulence-corrected, undistorted wave exits the fiber bundle 3.

1 fiber-optical system 2 detection unit 21 reference wave 3 fiber bundle 30 individual fiber 31 fiber bundle distal side 32 fiber bundle proximal side 33 wave bundle emerging from the distal side of wave 34 emerging at the proximal end, Wave 35 distorted by fiber bundle Wave 4 with corrected light disturbance 4 Illumination source 41 Flat wave emitted from illumination source 5 Beam splitter 51 Wave 52 reflected by beam splitter towards spatial light modulator By beam splitter Transmitted Waves 6 Spatial Light Modulators 61 Reflected by the Spatial Light Modulators and Waves 62 that illuminate the Individual Fibers Pre-Distorted Waves 7 Reflected by the Spatial Light Modulators 7 Translucent Mirrors 8 Guided Stars

Claims (19)

The method of illuminating and detecting an object (9) by means of light comprises at least the following method steps a) and b):
a) calibrating the coherent bundle (3) of the optical fiber, the method step a)
i) illuminating at least one of the freely selectable individual fibers (30) of the coherent bundle of optical fibers (3) with light from the proximal;
ii) at partially reflecting means (7) at a distance from the distal cross section of the bundle of optical fibers (3), such that a region of the bundle of optical fibers (3) is illuminated from the distal by reflected light; Reflecting light at least partially, an area comprising a plurality of individual fibers (30), the reflected light being emitted from the virtual image (8) of the individual fibers (30) illuminated At least partially reflect light,
iii) Spatial intensity distribution of reflected light transmitted and disturbed in the region illuminated from the distal end of the optical fiber bundle, and reflected light transmitted and disturbed in the region illuminated from the distal end of the optical fiber bundle Detecting one of a spatial intensity distribution of an interference pattern generated by coherently superimposing a reference wave on
iv) evaluating the detection data to at least directly extract a single phase difference ΔΦ of the reflected light transmitted and disturbed in the distally illuminated area of the bundle of optical fibers (3);
v) determining a system function that reflects the transmission characteristics of the region illuminated from the distal end of the fiber optic bundle (3);
vi) a bundle of optical fibers (3) repeating sub-method steps i) to v) to determine a system function that reflects the overall transmission characteristics;
Have,
b) correcting the disturbance of light, illuminating the entire bundle of optical fibers (3) with light from the proximal and detecting the object (9) placed on the optical path behind the partial reflection means (7); ,
Illuminate the entire fiber optic bundle (3) proximally with uncorrected light, then correct the light disturbance and detect the object (9) placed on the optical path behind the partial reflection means (7) And
To do one of the
The correction of the illumination disturbance is carried out in that an inverse function of the system function is added to the light emitted from the illumination system by interaction with the wavefront modulator (6) comprising a plurality of individually operable elements. Following the transmission of the bundle of optical fibers (3), the wave field corresponding largely to the wave field emitted to the illumination system is the object (9) arranged on the optical path behind the partial reflection means (7). Available to light up in the
The correction of illumination disturbances uses the inverse function of the system function, the spatial enhancement distribution of the light transmitted to the fiber bundle (3) and disturbed after interaction with the object (9), and the optical fiber It is executed in numerically correcting at least one of a spatial intensity distribution of an interference pattern generated by coherently superimposing a reference wave on reflected light transmitted to the bundle (3) and disturbed. A method of illuminating and detecting an object with light. In the lower method step i), at least two non-adjacent non-adjacent ones of the individual fibers (30) of the bundle of optical fibers (3) are illuminated simultaneously from the proximal side, by means of their images in the lower method step ii) Method according to claim 1, characterized in that at least two virtual images of the fibers (30) are produced and the non-overlapping regions of the optical fiber bundle (3) are illuminated from the distal end. In sub-method step i), at least one of the freely selectable individual fibers (30) is illuminated proximally by at least one first illumination source;
In method step b), the entire coherent fiber optic bundle (3) is illuminated proximally by a second illumination source without correcting or correcting for light disturbances, or sub-method step i B) illuminating at least one of the freely selectable individual fibers (30) from the proximal side, and of the method step b), without correcting or correcting the light disturbance of the whole bundle of optical fibers (30) The illumination of the light from the proximal side is performed by exactly one illumination source (4) and the light is at least for the purpose of illuminating the proximal side at least one of the freely selectable individual fibers (30). 3. A method according to claim 1, characterized in that it interacts with a wave front modulator (6) arranged in the light path between the illumination source (4) and the bundle (3) of coherent optical fibers. Method. The partially reflecting means (7) is characterized in that it reflects most of the light or transmits most of the light to the distal side of the bundle (3) of optical fibers, depending on the wavelength of the light. The method according to any one of claims 1 to 3. The partial reflection means (7) is characterized by reflecting most of the light or transmitting most of the light to the distal side of the optical fiber bundle (3) depending on the polarization state of the light. The method according to any one of claims 1 to 3, wherein Evaluating the detection data and extracting at least phase information of the reflected light transmitted and disturbed to the optical fiber bundle (3) are transmitted to the optical fiber bundle (3) and disturbed 6. A method according to any one of the preceding claims, characterized in that it is performed by digital holography of the spatial intensity distribution of the interference pattern generated interferenceally overlapping the reference wave. Evaluating the detection data and extracting from the spatial intensity distribution at least the phase information of the reflected light transmitted and disturbed to the optical fiber bundle (3) is carried out by numerical reconstruction by the phase recovery method. 6. A method according to any one of claims 1 to 5, characterized in that A method according to any one of the preceding claims, characterized in that a freely adjustable light pattern is generated at the distal end of the bundle (3) of optical fibers. In a fiber-optical system (1) which illuminates and detects an object (9) by means of light,
A coherent bundle of optical fibers (3),
An illumination system that illuminates the coherent bundle (3) of optical fibers from the proximal side;
Means for partially reflecting light (7) arranged in the optical path of the light emitted from the illumination system between the distal cross section of the bundle of optical fibers (3) and the object (9) at a distance from the distal cross section )When,
Spatial intensity distribution of light transmitted to the optical fiber bundle (3) and disturbed, and interference pattern generated by coherently superimposing a reference wave on the light transmitted to the optical fiber bundle (3) and disturbed Detecting means (2) for detecting one of the spatial intensity distributions of
A signal processing platform for at least evaluating the detected light and determining at least phase information of the light transmitted to the optical fiber bundle (3) and disturbed;
Equipped with
The illumination system illuminates at least one of the freely selectable individual fibers (30) of the bundle of optical fibers (3) to calibrate the bundle of optical fibers (3) and of the observation of the object (9) Is characterized in that it is designed to illuminate the whole of the optical fiber bundle (3),
Fiber-optical system (1). The illumination system comprises at least one illumination source (4) and a wave front modulator (6) comprising a plurality of individually actuatable elements, the wave front modulator (6) being close to the bundle of optical fibers (3) A plurality of elements of the wavefront modulator (6) arranged on the optical path between the cross-section and the at least one illumination source (4), for calibrating the bundle of optical fibers (3) 10. A device according to claim 9, characterized in that at least one of the freely selectable individual fibers (30) of the bundle of fibers (3) is orientable to be illuminated by the at least one illumination source (4). A fiber-optic system (1) according to claim 1. The illumination system comprises at least two illumination sources, at least one of the freely selectable individual fibers (30) of the bundle of optical fibers (3) being at least for the calibration of the bundle of optical fibers (3) A fiber according to claim 9, characterized in that it is illuminated by one first illumination source and the whole bundle of optical fibers (3) is illuminated by a second illumination source for observation of the object (9). An optical system. A wavefront modulator (6) comprising a plurality of individually actuable elements is arranged on the optical path between the proximal cross section of the optical fiber of the bundle (3) and the illumination system,
The reciprocal of the disturbance of light transmitted to the fiber optic bundle (3) is emitted from the illumination system to illuminate and detect the object (9) by reflection at multiple elements of the wavefront modulator (6). The elements according to any one of claims 9 to 11, characterized in that the elements of the wavefront modulator (6) are actuatable by the signal processing platform so as to be provided to unperturbed light. Fiber-optical system (1). 13. Adjustable light pattern is generated at the distal end of a bundle of optical fibers (3) by a plurality of individually actuable elements of a wavefront modulator (6). Fiber-optical system (1). The fiber-optic system (1) according to claim 12 or 13, characterized in that the wavefront modulator (6) is a digital local spatial light modulator. A fiber-optic system (1) according to any one of claims 9 to 14, characterized in that the light partially reflecting means (7) comprises a reflecting surface which acts as a wavelength dependent beam splitter. 15. The fiber-optic system (1) according to any one of claims 9 to 14, characterized in that the partial reflection means (7) of light comprises a reflecting surface that functions as a beam splitter depending on the polarization state. . A fiber-optic system (1) according to any one of claims 9 to 14, characterized in that the light partially reflecting means (7) comprises a semitransparent reflecting surface. The fiber-optic system (1) according to any one of claims 9 to 17, characterized in that the detection means (2) comprise a CCD camera or a CMOS sensor. 19. The fiber-optic system (1) according to any one of claims 9 to 18, characterized in that the signal processing platform comprises at least one of an FPGA (Field Programmable Gate Array) and an image processing unit.

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